I added the option now. But it seems my computers aren't getting the NETBIOS part. Or there is something changed in dhcp service.
When I try to ping to my computers, all of them referred to hostname.localdomain and returned IP address as 126.96.36.199 (which is belonged to OpenDNS that I used); not their internal IP addresses (192.168.x.x).
Before switched to version 2.0, pfSense 1.2.3 I could just reference my computers and printer with their hostname (NETBOIS name). Especially to my printer, my driver is setup with referencing to its NETBIOS name; now I should changed to its IP address.
One more note. All my computers/printer are using static mapping of the dhcp service from pfSense.